The present invention relates generally to an apparatus for generating electric power and, in particular, to an apparatus responsive to a modulated fluid stream for driving an electric generator.
The kinetic energy of blowing wind has long been converted to mechanical energy. Many different wind driven devices have been proposed and used for taking energy from the wind and transforming it into mechanical or electrical power. For example, windmills are used to operate a pump, grind grain and the like. The best known type of windmill is the typical farm device which is quite satisfactory for its normal intended use of driving a water pump since it can usually provide more water than is needed, even at low efficiency. Such windmills are large, cumbersome, and expensive in relation to the amount of useful work they produce. They have a multitude of very large blades which are directly driven by the relative wind which contacts them, the velocity of which is often so low that the blades can not move the load.
Another common type of windmill is the generally spherical "turbine" type rotor used widely on houses to evacuate hot air from attics and garages. These rotors have multiple blades set at an angle to catch the relative wind at one side and deflect the wind at the other side. Again, they are quite suitable for their intended purpose, but they are actuated by the wind at its normal velocity and produce so little power that they can not drive any appreciable load.
A major drawback of the windmill type devices is that in order to harness enough energy to drive an electric generator, the windmill has to be excessively large and located in an area of high constant wind. The size of the conventional blades results in a constant chopping sound which is distracting and becomes unpleasant and uncomfortable after a short period of time of operation.
Considerable research and development efforts have been expended in attempts to utilize energy generated by wind and water flow. Water wheels and squirrel cage type fins suffer the disadvantage in that only those blades on the side moving with the wind can be utilized while the blades moving in the opposite direction have to be shrouded. As stated above, large propeller type fins rotating in a vertical plane have been tested and tried for the production of energy, but they too suffer a number of disadvantages. First, for practical purposes, they must be of considerable diameter for effective energy production. This results in tremendous cylindrical forces which may cause vibration and even twisting or crystallization of metal propeller blades and/or destruction of the supporting tower. Even in the absence of damage, large propellers tend to be noisy and are, therefore, objectionable in a community. Moreover, the large propellers require high towers to provide ample clearance under the propeller tips and such towers are commonly deemed unsightly and objectionable for community use.
Various types of wind-propelled devices have been proposed, including windmills, paddle constructions, and propeller type devices, which have operated satisfactorily under ordinary wind conditions. However, some devices, while operating satisfactory under moderate wind conditions, are not able to withstand winds at high velocity. Devices which are moderately efficient at winds of a certain level, may have efficiencies which drop off sharply at velocities below or above that level. To produce optimum results, wind driven devices should be rapidly responsive to changes in wind direction and velocity, characteristics not commonly shared by prior art devices. Optimally, and especially with electrical generating wind-driven devices, such devices should be sensitive to load requirements and speed limitation.
Examples of fluid flow powered electrical generators are shown in:
U.S. Pat. No. 4,350,900, issued to Baughman, discloses a wind or water driven machine having a squirrel cage rotor with a vertical axis of rotation. A louver or damper is utilized to control the amount of wind flowing to the rotor.
U.S. Pat. No. 4,609,827, issued to Nepple, discloses a vertical axis wind powered generator having airfoil shaped vanes.
U.S. Pat. No. 4,764,683, issued to Coombes, discloses a wind powered generator having nacelles for directing the wind stream against the rotor vanes.